BMW, if you are insisting on using a y-connector and you are sure of what cables you want, why not have a y cable made up to the length you want. I have seen JPS and KCI y cables at over a meter in length. This would be a better way than inserting more connections in the system.
The downside would be is when you decide to sell the cables. What you can do is find out if they can be reterminated to standard cables and at what expense.
The downside would be is when you decide to sell the cables. What you can do is find out if they can be reterminated to standard cables and at what expense.